Amicus curiae
A Dictionary of Law · Henry Campbell Black · 1891
A Dictionary of Law
Lat. A friend of the court. A by-stander (usually a counsellor) who interposes and volunteers information upon some matter of law in regard to which the judge is doubtful or mistaken, or upon a matter of which the court may take judicial cognizance. When a judge is doubtful or mistaken in matter of law, a by-stander may inform the court thereof as amicus curiae. Counsel in court frequently act in this capacity when they happen to be in possession of a case which the judge has not seen, or does not at the moment remember.
Holthouse.
It is also applied to persons who have no right to appear in a suit, but are allowed to introduce evidence to protect their own interests.
11 Tex. 699, 701, 702.